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Several recent studies suggest that the home advantage, that is, the benefit competitors accrue from performing in familiar surroundings, was—at least temporarily—reduced in games played without spectators due to the COVID-19 Pandemic. These games played without fans during the Pandemic have been dubbed 'ghost games'. However, the majority of the research to date focus on soccer and no contributions have been provided for indoor sports, where the effect of the support of the fans might have a stronger impact than in outdoor arenas. In this paper, we try to fill this gap by investigating the effect of ghost games in basketball with a special focus on the possible reduction of the home advantage due to the absence of spectators inside the arena. In particular, we test (i) for the reduction of the home advantage in basketball, (ii) whether such reduction tends to disappear over time, (iii) if the bookmakers promptly adapt to such structural change or whether mispricing was created on the betting market. The results from a large data set covering all seasons since 2004 for the ten most popular and followed basketball leagues in Europe show, on the one hand, an overall significant reduction of the home advantage of around 5% and no evidence that suggests that this effect has been reduced at as teams became more accustomed to playing without fans; on the other hand, bookmakers appear to have anticipated such effect and priced home win in basketball matches accordingly, thus avoiding creating mispricing on betting markets. [ABSTRACT FROM AUTHOR]

This paper examines whether sports betting markets are semi-strong form efficient--i.e., whether new information is rapidly and completely incorporated into betting prices. We use news on ghost games in the top European football leagues due to the COVID-19 pandemic as a clean arrival of new public information. Because spectators are absent during ghost games, the home advantage is reduced, and we test whether this information is fully reflected in betting prices. Our results show that bookmakers and betting exchanges systematically overestimated a home team's winning probability during the first period of the ghost games, which suggests that betting markets are, at least temporally, not semi-strong form efficient. Examining different leagues, we find that our main results are driven by the German Bundesliga, which was the first league to resume operations. We exploit a betting strategy that yields a positive net payoff over more than one month. [ABSTRACT FROM AUTHOR]